(a) Field of the Invention
This invention pertains broadly to wood burning, prefabricated fireplaces, and more particularly to such fireplaces that can selectively heat one, or more, rooms via ductwork that extends throughout the several rooms of the structure in which the fireplace is situated.
(B) Prior Art
Masonry fireplaces, while presenting an aesthetically pleasing appearance, are expensive to build because of their massive footings, large chimneys, etc. and yet, function ineffectively. In an effort to construct fireplaces that can be assembled, installed and operated at a reduced cost, diverse manufacturers have turned to metal fireplaces which can be built, in large measure, in a factory by semi-automated techniques.
The more efficient metal fireplaces operate on a circulating air basis to provide sufficient air to maintain the combustion of the fuel placed in the firebox. Most of the so-called circulating fireplaces draw air into the firebox through grilles, suction air intakes, etc. communicating with the air in the room in which the fireplace is situated. The heat produced by the burning of the fuel, however, is radiated into the room, or, if properly vented, into immediately adjoining rooms. However, because of the rapid rise of heated air, the bulk of the heat quickly rises to the upper levels of the room, leaving the room unevenly heated.
Consequently, most metal fireplaces operating on the circulating principle, have proven to be but modestly successful in heating the room in which they are situated. However, because a significant part of the heat produced by the fireplace either travels up the flue and is vented to the atmosphere or rises quickly to the top of the room, these fireplaces have lacked the capability of heating remote areas in the same structure. Furthermore, known fireplaces have been unable to completely consume the fuel fed thereinto in a smoke free manner because of an insufficient flow of fresh air into and through the firebox.
In order to enhance the volume, and rate of flow of fresh air into the firebox for enhancing combustion, diverse techniques were employed. In U.S. Pat. No. 3,888,231, granted June 10, 1975 to Daniel T. Galluzo et al, the patent suggests elevating the fireplace on a hearth platform and disposing an air intake vent within the platform to draw additional air into the firebox from the room in which the fireplace is situated.
In U.S. Pat. No. 3,926,174, granted Dec. 16, 1975 to Ralph Bell, the patent utilizes a conduit, which is connected with the outside air through a vent in the upper part of the building foundation, for directing cool air through ports into the firebox to enhance combustion. The ports which direct the cool air into the fire are situated in a U-shaped wall member that surrounds the front of the fireplace. The vent in the building foundation, however, may allow undesirable seepage of cold air into the building when the fireplace is not operating.
In U.S. Pat. No. 4,010,728, granted Mar. 8, 1977, to Rod Hempel et al, the patent discloses a fireplace comprising three metalic shells having air spaces therebetween for cooling purposes, and a thermosyphonic chimney with three concentric members coupled to the respective shells of the fireplace. A tapered air-intake and a blower fan mounted adjacent to the intake, and seated on the roof of the building, force large quantities of cool air into the chimney. The cool air follows a circuituous path around the chimney, combustion dome and firebox, gathering heat all the time, then dumping the valuable hot air out into the atmosphere.
Although the commercially available version of Hempel et al fireplace functioned satisfactorily in most aspects, certain shortcomings were noted in actual field installations. For example, the blower and tapered air-intake had to be disposed on the roof of the structure in proximity to the chimney, or in attic space adjacent to the chimney; in either instance, the installation was cumbersome and time-consuming. Additionally, the fireplace, when operating near peak temperatures, tended to develop "hot spots" at the point where the flow through the chimney reverses direction and failed to produce a sufficient quantity of hot air to heat other rooms within the same structure. The down and then up travel of the air forced into the chimney also proved, in practice, to produce less than optimum results for much of the hot air was discharged into the atmosphere.
Although Hempel et al suggests venting heated air from the fireplace into adjacent rooms, no system is proposed for effectively distributing heated air to remote rooms within the structure and the distribution of the heated air might tend to diminish the effectiveness of the fireplace. The heated air, furthermore, lacked a sufficient pressure head to pass rapidly to remote rooms because of the length and location of the circuitous flow path through the chimney.